U.S. patent number 6,733,476 [Application Number 09/835,208] was granted by the patent office on 2004-05-11 for implantable drug delivery device with peristaltic pump having a bobbin roller assembly.
This patent grant is currently assigned to Medtronic, Inc.. Invention is credited to Steven R. Christenson, James M. Haase, Micheal Thomas Hegland, Mark S. Lent, William H. Monsen, James Randall.
United States Patent |
6,733,476 |
Christenson , et
al. |
May 11, 2004 |
Implantable drug delivery device with peristaltic pump having a
bobbin roller assembly
Abstract
An implantable drug infusion device includes a pump tube for
holding a liquid to be pumped. A race is configured to support the
pump tube. A roller assembly is configured to compress the tube
against the race at one or more points along the path, and the
roller assembly includes at least one roller. A drive assembly
drives the roller assembly relative to the tube along the path so
as to move the liquid through the tube. At least two biasing
members are operably connected to the roller to bias the roller
against the tube, the two biasing members forming an angle.
Inventors: |
Christenson; Steven R. (Coon
Rapids, MN), Randall; James (Coon Rapids, MN), Hegland;
Micheal Thomas (Mounds View, MN), Haase; James M.
(Blaine, MN), Lent; Mark S. (Brooklyn Park, MN), Monsen;
William H. (Rochester, MN) |
Assignee: |
Medtronic, Inc. (Minneapolis,
MN)
|
Family
ID: |
25268920 |
Appl.
No.: |
09/835,208 |
Filed: |
April 13, 2001 |
Current U.S.
Class: |
604/151;
417/477.1; 417/477.7 |
Current CPC
Class: |
A61M
5/14232 (20130101); F04B 43/1253 (20130101); F04B
43/1276 (20130101); A61M 5/14276 (20130101); A61M
2205/0266 (20130101) |
Current International
Class: |
A61M
5/142 (20060101); F04B 43/12 (20060101); A61M
001/00 () |
Field of
Search: |
;604/151,153,131
;417/477.3,477.7,477.1,474,476,423.6 |
References Cited
[Referenced By]
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Other References
US. patent application Ser. No. 09/834,874, entitled "Implantable
Drug Delivery Device with Peristaltic Pump Having a Retracting
Roller", filed Apr. 13, 2001, (P-9175.00). .
U.S. patent application Ser. No. 09/561,154, entitled, "Implantable
Drug Infusion Device with Peristaltic Pump using Tube Guide", filed
Apr. 28, 2000. (P-9176.00). .
U.S. patent application Ser. No. 09/561,583 entitled "Spring Loaded
Implantable Drug Infusion Device", filed Apr. 28, 2000.
(P-8901.00)..
|
Primary Examiner: Look; Edward K.
Assistant Examiner: Fristoe, Jr.; John K.
Attorney, Agent or Firm: Banner & Witcoff, Ltd.
Parent Case Text
RELATED APPLICATIONS
The following applications are related to the present application:
"Spring Loaded Implantable Drug Infusion Device", assigned Ser. No.
09/561,583 having Attorney Docket No. 11738.84231; and "Implantable
Drug Delivery Device with Peristaltic Pump Having Retractable
Rollers," assigned Ser. No. 09,834,874, having Attorney Docket No.
11738.86899.
Claims
What is claimed is:
1. An implantable drug infusion device comprising, in combination:
a pump tube for holding a liquid to be pumped; a race configured to
support the tube along a path; a roller assembly configured to
compress the tube against the race at one or more points along the
path, the roller assembly including at least one roller, the roller
assembly comprising at least two biasing members operably connected
to the roller to adjustably bias the roller against the tube, the
two biasing members forming an angle; and a drive assembly to drive
the roller assembly relative to the tube along the path so as to
move the liquid through the tube.
2. The implantable drug infusion device of claim 1, wherein at
least one of the biasing members comprises a coil spring.
3. The implantable drug infusion device of claim 1, wherein at
least one of the biasing members is made from a material selected
from the group consisting of cobalt, stainless steel, and nitinol
shape memory alloy.
4. The implantable drug infusion device of claim 1, wherein the two
biasing members each comprises a coil spring.
5. The implantable drug infusion device of claim 4, wherein the two
biasing members are made from a material selected from the group
consisting of cobalt, stainless steel, and nitinol shape memory
alloy.
6. The implantable drug infusion device of claim 1, wherein the
race includes an inlet ramp and an outlet ramp.
7. The implantable drug infusion device of claim 6, wherein the
inlet ramp has an arcuate geometry.
8. The implantable drug infusion device of claim 6, wherein the
outlet ramp has an arcuate geometry.
9. The implantable drug infusion device of claim 1, wherein the
roller assembly comprises at least one roller housing operably
connected to the two biasing members, each roller housing having a
roller secured thereto.
10. The implantable drug infusion device of claim 9, wherein the
roller assembly comprises three roller housings and three
rollers.
11. The implantable drug infusion device of claim 10, wherein each
biasing member comprises a coil spring.
12. The implantable drug infusion device of claim 9, wherein at
least one of the biasing members is made from a material selected
from the group consisting of cobalt, stainless steel, and nitinol
shape memory alloy.
13. The implantable drug infusion device of claim 1, wherein the
drive assembly comprises a drive shaft and a drive gear, the drive
gear configured to be rotatably driven by a motor, the drive shaft
rotatably driven by the drive gear and rotatably driving the roller
assembly.
14. The implantable drug infusion device of claim 13, wherein the
drive gear includes a plurality of teeth about a periphery of the
drive gear engageable by a gear of a motor assembly.
15. An implantable drug infusion device comprising, in combination:
a bulkhead having a race; a pump tube having an inlet and an outlet
and being positioned within the race; a roller assembly configured
to compress the tube against the race at one or more points along
the path, the roller assembly including at least one roller, the
roller assembly comprising at least two biasing members operably
connected to the roller to adjustably bias the roller against the
tube, the two biasing members forming an angle; and a drive
assembly to drive the roller assembly relative to the tube along
the path so as to move a liquid through the tube.
16. The implantable drug infusion device of claim 15, wherein at
least one of the biasing members comprises a coil spring.
17. The implantable drug infusion device of claim 15, wherein at
least one of the biasing members is made from a material selected
from the group consisting of cobalt, stainless steel, and nitinol
shape memory alloy.
18. The implantable drug infusion device of claim 15, wherein the
two biasing members each comprises a coil spring.
19. The implantable drug infusion device of claim 18, wherein the
two biasing members are made from a material selected from the
group consisting of cobalt, stainless steel, and nitinol shape
memory alloy.
20. The implantable drug infusion device of claim 15, further
comprising a support plate to secure the roller assembly and drive
assembly to the bulkhead.
21. The implantable drug infusion device of claim 15, further
comprising a motor assembly, the drive assembly driven by the motor
assembly.
22. An implantable drug infusion device comprising, in combination:
a bulkhead having a race, a first chamber, and a second chamber; a
pump tube having an inlet and an outlet and being positioned within
the race, the race configured to support the tube along a path; a
motor assembly positioned within the first chamber; and a pumphead
assembly positioned within the second chamber, the motor assembly
driving the pumphead assembly, the pumphead assembly comprising a
roller assembly having a hub, three roller housings, each roller
housing having a roller and being pivotally connected to the hub; a
drive assembly to drive the roller assembly relative to the tube
along the path so that the rollers compress the tube to move a
liquid through the tube; the rollers and race defining a gap; and
at least two springs operably connected to each roller housing to
bias a corresponding roller against the tube, the two springs
forming an angle.
23. The implantable drug infusion device of claim 22, wherein the
pumphead assembly further comprises a support plate secured to the
bulkhead.
24. The implantable drug infusion device of claim 22, wherein the
race includes an inlet ramp and an outlet ramp, the inlet ramp and
outlet ramp each having an arcuate geometry.
25. The implantable drug infusion device of claim 22, wherein the
springs are made from a material selected from the group consisting
of cobalt, stainless steel, and nitinol shape memory alloy.
26. An implantable drug infusion device comprising, in combination:
a pump tube for holding a liquid to be pumped; a race configured to
support the tube along a path; a roller assembly configured to
compress the tube against the race at one or more points along the
path, the roller assembly including at least two rollers and a hub,
the roller operably connected to at least one adjacent roller by a
biasing member to bias the roller against the tube, wherein the
roller, the adjacent roller and the hub form a triangle, and a
drive assembly to drive the roller assembly relative to the tube
along the path to move the liquid through the tube.
27. The implantable drug infusion device of claim 26, wherein the
roller is operably connected to a first adjacent roller by a first
biasing member, and the roller is operably connected to a second
adjacent roller by a second biasing member.
28. The implantable drug infusion device of claim 27, wherein the
first and second adjacent rollers are operably connected by a third
biasing member.
29. The implantable drug infusion device of claim 26, wherein the
biasing member is a coil spring.
30. The implantable drug infusion device of claim 26, wherein the
biasing member is made from a material selected from the group
consisting of cobalt, stainless steel, and nitinol shape memory
alloy.
31. The implantable drug infusion device of claim 26, wherein the
drive assembly comprises a drive shaft, and a drive gear, the drive
gear configured to be rotatably driven by a motor, the drive shaft
rotatably driven by the drive gear and rotatably driving the roller
assembly.
32. The implantable drug infusion device of claim 31, wherein the
drive gear includes a plurality of teeth about a periphery of the
drive gear to engage a gear of a motor assembly.
33. The implantable drug infusion device of claim 26, further
comprising a bulkhead and a support plate to secure the roller
assembly and drive assembly to the bulkhead.
34. An implantable drug infusion device comprising, in combination:
a pump tube for holding a liquid to be pumped; a race configured to
support the tube along a path, the race having a center; a roller
assembly configured to compress the tube against the race at one or
more points along the path, the roller assembly including at least
two rollers and a hub, the hub having a center, each roller
operably and pivotally connected to the hub by a corresponding
retracting roller arm and a corresponding biasing member to bias
each roller against the tube, wherein the rollers and the hub form
a triangle, each corresponding retracting roller arm and
corresponding biasing member forming an angle, each roller located
at one end of its corresponding retracting roller arm, a drive
assembly to drive the roller assembly relative to the tube along
the path to move the liquid through the tube, the center of the hub
substantially coinciding with the center of the race, the load of
the rollers on the tube being substantially uniform.
35. The implantable drug infusion device of claim 34, wherein the
biasing member is a coil spring.
36. The implantable drug infusion device of claim 34, wherein the
biasing member is made from a material selected from the group
consisting of cobalt, stainless steel, and nitinol shape memory
alloy.
37. The implantable drug infusion device of claim 34, wherein the
roller arm assembly comprises three rollers and corresponding
retracting roller arms and biasing members to bias each roller
against the tube.
38. The implantable drug infusion device of claim 34, wherein the
drive assembly comprises a drive shaft, and a drive gear, the drive
gear configured to be rotatably driven by a motor, the drive shaft
rotatably driven by the drive gear and rotatably driving the roller
assembly.
39. The implantable drug infusion device of claim 38, wherein the
drive gear includes a plurality of teeth about a periphery of the
drive gear to engage a gear of a motor assembly.
40. The implantable drug infusion device of claim 34, further
comprising a bulkhead and a support plate to secure the roller
assembly and drive assembly to the bulkhead.
Description
FIELD OF THE INVENTION
The present invention relates to an implantable drug delivery
device for infusing a therapeutic agent into an organism, and more
particularly, relates to an improved peristaltic implantable pump
with improved occlusion along a drug delivery pump tube.
BACKGROUND OF THE INVENTION
Implantable drug infusion devices are well known in the art. These
devices typically include a medication reservoir within a generally
cylindrical housing. Some form of fluid flow control is also
provided to control or regulate the flow of fluid medication from
the reservoir to the outlet of the device for delivery of the
medication to the desired location in a body, usually through a
catheter. These devices are used to provide patients with a
prolonged dosage or infusion of a drug or other therapeutic
agent.
Active drug infusion devices feature a pump or a metering system to
deliver the drug into the patients system. An example of such a
drug infusion pump currently available is the Medtronic SynchroMed
programmable pump. Additionally, U.S. Pat. Nos. 4,692,147 (Duggan),
5,840,069 (Robinson), and 6,036,459 (Robinson), assigned to
Medtronic, Inc., Minneapolis, Minn., disclose body-implantable
electronic drug administration devices comprising a peristaltic
(roller) pump for metering a measured amount of drug in response to
an electronic pulse generated by control circuitry associated
within the device. Each of these patents is incorporated herein by
reference in their entirety for all purposes. Such devices
typically include a drug reservoir, a fill port, a peristaltic pump
having a motor and a pumphead to pump out the drug from the
reservoir, and a catheter port to transport the drug from the
reservoir via the pump to a patient's anatomy. The drug reservoir,
fill port, peristaltic pump, and catheter port are generally held
in a housing, or bulkhead. The bulkhead typically has a series of
passages extending from the drug reservoir and through the
peristaltic pump that lead to the catheter port, which is typically
located on the side of the housing. The peristaltic pump comprises
a pumphead having rollers, a race or cavity defined by the
bulkhead, and a pump tube that is threaded or inserted between the
rollers and the race. The peristaltic pumps use the rollers to move
a drug through the pump tube from the drug reservoir to the
catheter port. The drug is then pushed by the pump through a
catheter connected to the catheter port, and is delivered to a
targeted patient site from a distal end of the catheter.
The prior art delivery devices, however, are limiting in that the
load that the rollers place on the tube can vary as the rollers
move along the tube. If the load is excessive, excess energy will
be consumed and the tube life will be shortened, resulting in
increased replacement costs. If the load is insufficient,
inadequate occlusion of the tube will result in leakage of fluid
past the roller, reducing the accuracy of the pump. Variation in
the load is caused by variations in the gap between the rollers and
the race in which the pump tube lies, the gap variance being due to
manufacturing tolerances associated with the tube, the race and the
pumphead. Prior art solutions to the load variance problem include
tight manufacturing tolerances, sorting and matching of components,
and placing shims of appropriate thickness between the rollers and
the tube, each of which increases manufacturing costs and reduces
manufacturing flexibility.
It is an object of the present invention to provide an implantable
drug infusion device which reduces or wholly overcomes some or all
of the difficulties inherent in prior known devices. Particular
objects and advantages of the invention will be apparent to those
skilled in the art, that is, those who are knowledgeable or
experienced in this field of technology, in view of the following
disclosure of the invention and detailed description of preferred
embodiments.
SUMMARY OF THE INVENTION
The present invention provides an implantable drug infusion device
which features a peristaltic pump having a new configuration, in
which a spring biases a roller assembly against a pump tube,
thereby minimizing the variation in the load that the roller
assembly places on the pump tube.
In accordance with a first aspect, an implantable drug infusion
device comprises a peristaltic pump, including a pump tube for
holding a liquid to be pumped. A race is configured to support the
tube along a path. A roller assembly is configured to compress the
tube against the race at one or more points along the path, and the
roller assembly includes at least one roller. A drive assembly
drives the roller assembly relative to the tube along the path so
as to move the liquid through the tube. A biasing member is
operably connected to the one roller to adjustably bias the roller
against the tube.
In accordance with another aspect, an implantable drug infusion
device includes a bulkhead having a race. A pump tube having an
inlet and an outlet is positioned within the race, the race
configured to support the tube along a path. A roller assembly is
configured to compress the tube against the race at least one point
along the path, and the roller assembly includes a hub and at least
one roller biased against the pump tube. A drive assembly drives
the roller assembly relative to the tube along the path so as to
move a liquid through the tube. A biasing member is operably
connected to the roller to adjustably bias the at least one roller
against the tube.
In accordance with yet another aspect, an implantable drug infusion
device includes a bulkhead having a race, a first chamber, and a
second chamber. A pump tube has an inlet and an outlet and is
positioned within the race, the race configured to support the tube
along a path. A motor assembly is positioned within the first
chamber, a pumphead assembly is positioned within the second
chamber, and the motor assembly drives the pumphead assembly. A
drive assembly drives the roller assembly relative to the tube
along the path so the rollers compress the tube to move a liquid
through the tube. A spring is operably connected to each roller
assembly to bias a corresponding roller against the tube.
In accordance with another aspect, the pumphead assembly includes a
roller assembly comprising at least two biasing members or springs
operably connected to each roller to adjustably bias the roller
against the pump tube, wherein the biasing members form an angle.
This roller assembly provides biasing or spring loading to the
rollers that provide occlusion to the pump tube and thus move a
drug through the pump tube. In a preferred embodiment, the roller
assembly comprises three rollers contained within three
corresponding roller housings, each roller housing operably
connected to the other two roller housings by a biasing member or
spring. Thus, at each roller housing is a pair of operably
connected biasing members or springs, which form an angle. This
triangular arrangement of springs provides a compact design with a
low spring rate at each roller. The low spring rate at each roller
provides for low variations in occlusion load and for changes in
roller distance from the pump shaft. This triangular spring
arrangement can be characterized as a "live" bobbin roller
assembly, wherein each roller housing is operably connected to an
adjacent roller housing by a biasing member or spring. Further,
components or parts for this bobbin roller assembly can be readily
made using injection molding processing. More specifically, the
parts that can be readily made using injection molding processing
include an upper plate, a lower plate, and the three roller
housings.
From the foregoing disclosure, it will be readily apparent to those
skilled in the art, that is, those who are knowledgeable or
experienced in this area of technology, that the present invention
provides a significant advance over the prior art. Preferred
embodiments of the implantable infusion device of the present
invention can significantly reduce the variation in load placed by
the roller assembly on the pump tube. This will allow for less
stringent manufacturing tolerances, increased manufacturing
flexibility, increased tube life, and improved performance. These
and additional features and advantages of the invention disclosed
here will be further understood from the following detailed
disclosure of preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments are described in detail below with reference
to the appended drawings.
The accompanying drawings, which are incorporated into and form a
part of this specification, together with the description, serve to
explain the principles of the invention. The drawings are not drawn
necessarily to scale, are only for the purpose of illustrating a
preferred embodiment of the invention, and are not to be construed
as limiting the invention. Some features of the implantable drug
delivery device depicted in the drawings have been enlarged or
distorted relative to others to facilitate explanation and
understanding. The above mentioned and other advantages and
features of the invention will become apparent upon reading the
following detailed description and referring to the accompanying
drawings in which like numbers refer to like parts throughout and
in which:
FIG. 1 is an exploded perspective view of an implantable drug
delivery device in accordance with the present invention;
FIG. 2 is an exploded perspective view of a pumphead assembly of
the implantable device of FIG. 1;
FIG. 3 is perspective view, partially cut away, of the implantable
device of FIG. 1 shown in its assembled state;
FIG. 4 is a section view, taken along lines 4--4 of FIG. 3, of the
implantable device of FIG. 1;
FIG. 5 is a section view, taken along lines 5--5 of FIG. 2, of a
retracting roller arm of the implantable device of FIG. 1;
FIG. 6 is an exploded perspective view of an alternative embodiment
of the roller arm assembly of FIG. 1;
FIG. 7 is a plan view of the geometry of the race and inlet and
outlet ramps of the implantable device of FIG. 1;
FIG. 8 is an exploded perspective view of an alternative
embodiment, sometimes referred to herein as the bobbin embodiment,
to the roller arm assembly 20 shown in FIG. 2;
FIG. 9 is a perspective view of the bobbin embodiment shown in FIG.
8 as assembled, without an upper plate shown;
FIG. 10 is a perspective view of the bobbin embodiment of the
present invention shown in FIG. 9, illustrating the attachment of
an upper plate;
FIG. 11 is a top view of the bobbin embodiment illustrated in FIG.
10;
FIG. 12 is section view, taken along lines 12--12 of FIG. 11;
FIG. 13 illustrates roller bobbin housing loads for the condition
of nominal spring loads;
FIG. 14 illustrates bobbin housing loads with lagging spring 10%
low in load and leading spring 10% high in load;
FIG. 15 illustrates bobbin housing loads with leading spring 10%
low in load and lagging spring 10% high in load; and
FIG. 16 illustrates bobbin housing loads for the condition of
lagging spring removed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in FIG. 1, an implantable drug delivery device 2 in
accordance with the invention comprises a bulkhead 4 containing a
number of chambers and cavities sized and configured to house
various subsystems of the implantable drug infusion device. In
particular, bulkhead 4 has a first chamber 6 sized and configured
to house a peristaltic pumphead assembly 8. A second chamber 10,
sized and configured to house a motor assembly 12 which drives
pumphead assembly 8, is positioned adjacent first chamber 6 and
separated therefrom by a wall 13. Other chambers of bulkhead 4
house a battery and the electronic circuitry (not shown) used to
operate implantable drug infusion device 2 and to control the
dosage rate of the medication into the body.
Pumphead assembly 8 includes a compression member, such as roller
arm assembly 20, for compressing a pump tube 14 having an inlet 16
and an outlet 18. First chamber 6 has a generally circular wall 24
defining a pump race 19. Pump tube 14 is placed in first chamber 6
in close proximity to wall 24 so that roller arm assembly 20 may
force the tube against the wall, thereby forcing medication to move
through the tube in a known peristaltic manner. Flanges 21
extending outwardly from pumphead assembly 8 are received in
recesses 23 formed in first chamber 6, supporting pumphead assembly
8 in first chamber 6. Inlet 16 is placed in a pump inlet cavity 26
formed in bulkhead 4. Pump inlet cavity 26 is connected to the pump
race 19 by a pump inlet race ramp 28. Pump tube outlet 18 is placed
in a pump outlet cavity 30 formed in bulkhead 4. Pump tube outlet
cavity 30 is connected to the pump race 19 by a pump outlet race
ramp 32. In a preferred embodiment, both pump inlet race ramp 28
and pump outlet race ramp 32 have an arcuate geometry to reduce
pumphead torque as described in greater detail below. A cover (not
shown) is also provided for bulkhead 4 to provide protection for
the components of drug infusion device 2. Motor assembly 12
includes a motor (not shown) which drives a four-stage gear
assembly 11, only the fourth stage of which is visible. Teeth 15
are formed on the periphery of the fourth stage of gear assembly
11.
Bulkhead 4 has an integral fill port cavity 34, sized and
configured to house a septum and components to retain the septum.
Drugs are injected through the septum to fill a reservoir (not
shown) contained within a lower portion of bulkhead 4. A pathway is
formed between the reservoir and pump inlet cavity 26, through
which drugs are introduced into pump tube 14. The drugs exit pump
outlet cavity 30 and travel through another pathway formed in
bulkhead 4 to a catheter port on the periphery of bulkhead 4 from
which the drug exits the device 2 and enters the anatomy of the
individual. The structure of the septum, retaining components,
pathways, and catheter port are known to one of skill in the art
and are not shown here.
Referring now to FIG. 2, pumphead assembly 8 is shown in exploded
form. Pumphead assembly 8 includes a drive gear 40 with teeth 44
formed about its periphery. A support plate 42 is positioned below
drive gear 40. Flanges 21 extend outwardly from support plate 42
and, as described above, are received in recesses 23 of bulkhead 4,
and preferably welded thereto. Roller arm assembly 20 is positioned
below support plate 42. Drive shaft 46 extends axially through
apertures in roller arm assembly 20, support plate 42, and drive
gear 40, and is retained by retaining screw 48. Drive shaft 46 is
supported for rotation at its lower end by lower bearing 50, and at
a central location, between roller arm assembly 20 and support
plate 42, by upper bearing 52.
Roller arm assembly 20 comprises a central hub 53 having an
aperture 55 through which drive shaft 46 extends. Flat 57 on drive
shaft 46 mates with flat 59 of aperture 55 such that roller arm
assembly 20 rotates as drive shaft 46 rotates. A plurality of
roller arms 54 are each pivotally secured by a pin 56 to hub 53.
Each roller arm 54 comprises upper plate 51 and lower plate 61. A
roller 58 is pivotally secured to each roller arm 54 by an axle 60.
As seen in FIG. 5, axle 60 extends between upper plate 51 and
corresponding lower plate 61. Axle 60 passes through an inner race
(not shown) of roller 58. In the illustrated embodiment, roller arm
assembly 20 is shown with three roller arms 54 and three
corresponding rollers 58, however, the number of roller arms 54 and
rollers 58 may be greater or lesser than three.
As seen in FIGS. 3 and 4, teeth 15 of gear assembly 11 drivingly
engage teeth 44 of drive gear 40, thereby causing rollers 58 to
move about race 19, compressing and occluding tube 14 as they move
and forcing the drug therethrough in known peristaltic fashion. As
noted above, inlet race ramp 28 and outlet race ramp 32 each have
an arcuate geometry, which reduces the torque required as each
roller 58 engages pump tube 14 during rotation of roller arm
assembly 20.
Referring back to FIG. 2, each roller arm 54 and its corresponding
roller 58 is adjustably biased outwardly by a biasing member, such
as spring 62. In a preferred embodiment, spring 62 is a coil
spring. As seen in FIG. 4, spring 62 is oriented to facilitate the
occlusion, or compression, of tube 14 by roller 58. Since
manufacturing tolerances on the system components, i.e., roller 58,
tube 14 and race 19, can result in variations in the gap A between
roller 58 and race 19, the biasing action of spring 62 can
advantageously minimize the variation in load placed by roller 58
on tube 14, greatly increasing the compliance of the system. Thus,
for an incremental change in the gap between roller 58 and race 19,
the incremental load required is reduced. For example, in prior art
devices, where the system compliance is accounted for by the tube
itself, a 0.001" decrease in a radial direction of the race could
incur a 150 g load increase on roller 58. With the present
invention, however, spring 62 may be sized with a spring rate such
that for a 0.001" decrease in the race, a 1.5 g increase in load is
realized. In a preferred embodiment, spring 62 is formed of a
highly corrosion resistant and fatigue resistant alloy. Suitable
materials for biasing member or spring 62 include cobalt and
stainless steel alloys. In other preferred embodiments, a nitinol
shape memory alloy may be used for spring 62.
The biasing member provides numerous advantages over the prior art
devices. Reducing the variation in load prevents excessive loading,
thereby providing increased tube life; minimizes the force needed
to occlude the pump tube, thereby minimizing the torque requirement
for occlusion; improves occlusion and, therefore, reducing leakage
and improving the performance of the peristaltic pump; allows for
looser manufacturing tolerances and minimizes the need for sorting
and matching components, providing increased manufacturing
flexibility and reducing costs.
In an embodiment, as seen in FIG. 2, roller arm assembly 20 further
includes a tube guide 66. In the illustrated embodiment, tube guide
66 is connected to roller arm 54 and is formed of an upper plate 68
and a lower plate 70. In another embodiment, tube guide 66 may be
connected directly to hub 53. Tube guide 66 serves to help keep
pump tube 14 properly aligned to ensure that rollers 58 are
centered with respect to pump tube 14.
Another embodiment of a roller arm assembly 80 is shown in FIG. 6.
Roller arm assembly 80 comprises three roller arms 82 pivotally
secured to a hub 84. Hub 84 comprises upper plate 86, lower plate
88, and center plate 90. Rods 92 extend through apertures 94, 95,
and 96 formed in upper plate 86, center plate 90, and lower plate
88, respectively. Pivot pins 98 extend between upper plate 51' and
lower plate 61' of each roller arm 82. Hooks 100, 102 formed on
upper plate 86 and lower plate 88, respectively, of hub 84, capture
pivot pins 98. The force of springs 62 acting on roller arms 82
helps maintain roller arms 82 in position on hub 84.
In a preferred embodiment, inlet and outlet ramps 28 and 32 have
exit and entry ramps transitioning smoothly into and from race 19
in order to minimize drag torque on pumphead assembly 8. As seen in
FIG. 7, inlet ramp 28 transitions smoothly from a radius R of
approximately 3.947 mm (0.1554 in) through point B to point A of
race 19. Race 19 then transitions from point A' to point B and then
through a radius R{character pullout} of approximately 4.02 mm
(0.1583 mm). The angles D, D' between points A and B, and
A{character pullout} and B{character pullout}, respectively are
approximately 35.5 degrees. Shown in the table below are the
dimensions for the radius of race 19 along the arc between points A
and B, and A{character pullout} and B{character pullout}, in 0.5
degree increments. It is to be appreciated that the radius varies
smoothly along race 19.
Angle (degrees) Radius 0.0.degree. 11.0000 .5 11.0054 1.0 11.0108
1.5 11.0162 2.0 11.0216 2.5 11.0270 3.0 11.0324 3.5 11.0378 4.0
11.0432 4.5 11.0486 5.0 11.0540 5.5 11.0594 6.0 11.0648 6.5 11.0702
7.0 11.0756 7.5 11.0810 8.0 11.0864 8.5 11.0918 9.0 11.0972 9.5
11.1026 10.0 11.1080 10.5 11.1134 11.0 11.1188 11.5 11.1242 12.0
11.1296 12.5 11.1350 13.0 11.1404 13.5 11.1458 14.0 11.1512 14.5
11.1566 15.0 11.1620 15.5 11.1674 16.0 11.1728 16.5 11.1782 17.0
11.1836 17.5 11.1890 18.0 11.1944 18.5 11.1998 19.0 11.2052 19.5
11.2106 20.0 11.2160 20.5 11.2214 21.0 11.2268 21.5 11.2322 22.0
11.2376 22.5 11.2430 23.0 11.2484 23.5 11.2538 24.0 11.2592 24.5
11.2646 25.0 11.2700 25.5 11.2754 26.0 11.2808 26.5 11.2862 27.0
11.2916 27.5 11.2970 28.0 11.3024 28.5 11.3078 29.0 11.3132 29.5
11.3186 30.0 11.3240 30.5 11.3294 31.0 11.3348 31.5 11.3402 32.0
11.3456 32.5 11.3510 33.0 11.3564 33.5 11.3618 34.0 11.3672 34.5
11.3726 35.0 11.3780 35.5 11.3834
An alternative embodiment, which can be referred to as the bobbin
embodiment, is illustrated in FIGS. 8 through 16. In this
embodiment, a roller assembly 500 is assembled and can replace
roller arm assembly 20 in FIG. 2. Thus, roller assembly 500 is
configured to compress pump tube 14 against the race 19 at one or
more points along a path. The roller assembly 500 comprises at
least one roller 404, and at least two biasing members or springs
402 operably connected to the roller 404 to adjustably bias the
roller 404 against the tube 14. The two biasing members 402 form an
angle 501. Further, roller housings 400 are connected to at least
one adjacent roller housing 400 by a spring 402.
As illustrated in FIGS. 8 through 12, rollers 404 are positioned
within a corresponding roller housing 400. In this embodiment,
rollers 404, roller pins 405, roller housings 400 and springs 402
are positioned between a lower plate 406 and an upper plate 408.
Lower plate 406 and upper plate 408 define openings 409 to receive
portions 410 and 412 of roller housings 400, respectively. Portions
410 and 412 of roller housings 400 are positioned within openings
409 and are nearly flush with bottom surface 414 of bottom plate
406, and top surface 416 of upper plate 408, respectively. Roller
pins 405 can be pressed or staked into roller housing 400, with
spacers 407 providing a gap between roller 404 and roller housing
400.
Hub 418 is comprised of portion 420 of bottom plate 406 and portion
421 of upper plate 408. Portions 420 and 421 can mate with each
other via mating member 422 of bottom plate 406 and a corresponding
mating member 423 of upper plate 408. FIG. 8 shows each mating
member 423 lined up and between the center of hub 418 and a
corresponding roller pin 405 to form a straight line. This
embodiment provides structure to encapsulate springs 402 to avoid
potential contact between springs 402 and pump tube 14. Shaft 424
can be placed through hole 425 defined in bottom plate 406 and
through hole 426 in top plate 408. Shaft 424 can be driven by a
drive assembly (not shown) as described in the preceding
embodiments.
FIG. 13 illustrates roller bobbin housing loads for the condition
of nominal spring loads.
FIG. 14, illustrates bobbin housing loads with lagging spring 10%
low in load and leading spring 10% high in load.
FIG. 15 illustrates bobbin housing loads with leading spring 10%
low in load and lagging spring 10% high in load.
FIG. 16 illustrates bobbin housing loads for the condition of
lagging spring removed.
Referring back to FIGS. 8 through 12, each roller housing 400 and
its corresponding roller 404 is adjustably biased outwardly by at
least two biasing members or springs 402. In addition, roller
housings 400 can also be operably connected to hub 418, such as by
springs similar to springs 402, including springs 62 as shown in
FIGS. 2, 4, and 6.
In a preferred embodiment, spring 402 is a coil spring. In a
preferred embodiment, spring 402 is formed of a material selected
from the group consisting of cobalt, stainless steel or a nitinol
shape memory alloy.
As shown in FIGS. 8-12, at least two springs 402 are oriented to
facilitate the occlusion, or compression, of pump tube 14 by a
roller 404. Since manufacturing tolerances on the system
components, i.e., roller 404, tube 14 and race 19, can result in
variations in the gap A between roller 404 and race 19, the biasing
action of spring 402 can advantageously minimize the variation in
load placed by roller 404 on tube 14, greatly increasing the
compliance of the system. Thus, for an incremental change in the
gap between roller 404 and race 19, the incremental load required
is reduced. For example, in prior art devices, where the system
compliance is accounted for by the tube itself, a 0.001" decrease
in a radial direction of the race could incur a 150 g load increase
on roller 404. With the present invention, however, spring 402 may
be sized with a spring rate such that for a 0.001" decrease in the
race, a 1.5 g or less increase in load is realized.
The bobbin embodiments illustrated in FIGS. 8 through 16, and as
described above, provides numerous advantages over the prior art
devices. Reducing the variation in load (a) prevents excessive
loading, thereby providing increased tube life, and minimizes the
force needed to occlude the pump tube, thereby minimizing the
torque requirement for occlusion; (b) improves occlusion therefore,
reducing leakage and improving the performance of the peristaltic
pump; and (c) allows for looser manufacturing tolerances and
minimizes the need for sorting and matching components, providing
increased manufacturing flexibility and reducing costs.
It is to be appreciated that other roller arm and/or bobbin
assembly constructions will be suitable, and are considered within
the scope of the present invention. Suitable roller arm and/or
bobbin assembly constructions will provide a biasing member or
combination of biasing members to ensure that a roller, or other
suitable compression member, is biased against a pump tube, thereby
minimizing the variation in load required to occlude the pump
tube.
Other suitable biasing members include, for example, leaf springs
and springs of other constructions, elastomeric members, closed or
open cell elastomeric foam members, torsion bars, magnetic members,
and solenoids.
In light of the foregoing disclosure of the invention and
description of the preferred embodiments, those skilled in this
area of technology will readily understand that various
modifications and adaptations can be made without departing from
the scope and spirit of the invention. All such modifications and
adaptations are intended to be covered by the following claims.
* * * * *